title: Effects of oriented surface dipole on photoconversion efficiency in an alkane/lipid-hybrid-bilayer-based photovoltaic model system.
abstract: When a phospholipid monolayer containing a zinc-coordinated porphyrin species formed atop a self-assembled monolayer of heptadecafluoro-1-decanethiol (CF3(CF2)7(CH2)2SH) is subjected to photoelectrochemical current generation, a significant modulation effect is observed. Compared with devices that contain similar photoactive lipid monolayers but formed on 1-dodecanethiol SAMs, these fluorinated hybrid bilayers produce a >60% increase in cathodic currents and a similar decrease in anodic currents. Photovoltages recorded from these hybrid bilayers are found to vary in the same fashion. The modulation of photovoltaic responses in these hybrid-bilayer-based devices is explained by the opposite surface dipoles associated with the thiols employed in this study, which in one case (fluorothiol) increase and in another (alkanethiol) decrease the work function of the underlying gold substrates. A similar trend of photovoltage/photocurrent modulation is also observed if fullerene is used as the photoagent in these devices. Our results reveal the intricacy of orientated surface dipole in influencing the photovoltaic processes, and its subtle interplay with other factors related to the photoagents, such as their location and orientation within the organic matrix.
authors.affiliation: Department of Chemistry and Biochemistry, Auburn University, Auburn, AL 36849, USA.
authors.forename: Lixia
authors.initials: L
authors.lastname: Liu
authors.forename: Hong
authors.initials: H
authors.lastname: Xie
authors.forename: Heidi E
authors.initials: HE
authors.lastname: Bostic
authors.forename: Limei
authors.initials: L
authors.lastname: Jin
authors.forename: Michael D
authors.initials: MD
authors.lastname: Best
authors.forename: X Peter
authors.initials: XP
authors.lastname: Zhang
authors.forename: Wei
authors.initials: W
authors.lastname: Zhan
mesh_terms: D000473:Alkanes / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D011166:Porphyrins / Q000737:chemistry; D012993:Solar Energy; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry
chemical_list: D000473:Alkanes; D008051:Lipid Bilayers; D011166:Porphyrins; D013438:Sulfhydryl Compounds; D015032:Zinc
keywords: charge-carrier injection; electrochemistry; lipids; magnetic properties; self-assembly